BeginnerTopic 1 of 106Electrical Engineering
Electric charge
The fundamental property of matter that causes electric forces; measured in coulombs.
In depth
Charge is a conserved property that comes in positive and negative forms; like charges repel and unlike attract. The elementary charge is 1.602×10⁻¹⁹ C, carried by electrons and protons. Charge moves easily in conductors and is trapped in insulators.
Key points
- Unit: coulomb (C)
- Charge is quantised
- Static electricity is charge imbalance
ExampleOne ampere-second equals one coulomb, about 6.24×10¹⁸ electrons.
All electrical behaviour comes from charge, so every current, voltage and force in a circuit traces back to this basic quantity.
What is Electric charge?
The fundamental property of matter that causes electric forces; measured in coulombs.
Why is it important to understand electric charge?
All electrical behaviour comes from charge, so every current, voltage and force in a circuit traces back to this basic quantity.
What is the unit of charge?
The coulomb, equal to the charge carried by about 6.24 times ten to the eighteenth electrons.
Why are electrons negative?
It is a convention set by Franklin. Current is conventionally shown as flowing from positive to negative, although electrons actually move the other way.
How is Electric charge used in practice?
Typical applications include explaining why static electricity can damage a microchip, sizing the charge stored in a battery pack and understanding why like charges repel in a capacitor.
What should I learn before Electric charge?
It is the first topic in Electrical Engineering, so no earlier topic in this course is required.
What are the key points of Electric charge?
Unit: coulomb (C). Charge is quantised. Static electricity is charge imbalance.
Can you give an example of Electric charge?
One ampere-second equals one coulomb, about 6.24×10¹⁸ electrons.
What comes after Electric charge?
The next topic is "Current", which builds directly on this one.
How difficult is Electric charge?
It is classed as Beginner in Electrical Engineering (topic 1 of 106). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.